Numbers 30:7

And her husband heard it, and held his peace at her in the day that he heard it,.... The vow she made, and by his silence consented to it:

then her vows shall stand, and her bonds wherewith she…

It is here taken for granted that all such persons as are sui juris - at their own disposal, and are likewise of sound understanding and memory, are bound to perform whatever they vow that is lawful…

When her husband comes to hear of it (see Num 30:30), he may then either annul it if he wishes, or by tacit approval allow it to stand.